[Simple-support] RegistryStrategy causes NPE when Converter is used

[Shevek <sh...@an...>]

Test case is a bit tangled, but I can provide it if the explanation
below isn't sufficient:

* Interface Value has a method getType() which returns the type of the
value.

* However ArrayValue implements this to return the type of the element,
not the array type. See TreeStrategy.read() lines circa 105, where
'actual', not 'expect' is passed to readArray().

* This causes RegistryStrategy's read() method to call lookup() with an
element type, and return a Converter when it is actually holding the
array node, not the element node.

* This causes the Converter to fail, since it gets given the InputNode
for the array itself, not the InputNode for the array element, and so
the attributes expected are not present.

Possible solutions:

1) Pass 'actual', not 'expect' to ArrayValue. This makes ArrayValue
satisfy the contract of Value, but may break things which rely on
ArrayValue being a special case.

2) During deserialization, at the point where RegistryStrategy calls
lookup(), make it ignore Value.getType(), since that is invalid, and
rely on the expected type if present. This may still have to use
Value.getType() during serialization...

3) ... ?

Any guidance?

S.